Method for manufacturing colored particle dispersion

Abstract

The present invention provides [1] a process for producing a colored fine particle dispersion including the step of subjecting a dispersion including a pigment, a polymerizable monomer, a surfactant, a polymerization initiator and water to emulsion polymerization, the pigment being a pigment having a quinacridone skeleton; the surfactant being an anionic or nonionic surfactant; and the polymerization initiator including an anionic or nonionic azo-based compound, [2] a colored fine particle dispersion including colored fine particles having an average particle size of not less than 10 nm and not more than 300 nm, and [3] a process for producing a water-based ink for ink-jet printing, including the step of mixing the obtained colored fine particle dispersion and an organic solvent B.

The invention claimed is: 
     
       1. A process for producing a colored fine particle dispersion comprising a step of subjecting a dispersion comprising a pigment, a polymerizable monomer, a surfactant, a polymerization initiator and water to an emulsion polymerization,
 the pigment being a pigment having a quinacridone skeleton; 
 the surfactant being an anionic or nonionic surfactant; 
 the polymerization initiator comprising at least one carboxy group-containing azo compound selected from the group consisting of an azobiscarboxylic acid having 8 to 16 carbon atoms, an azobiscyanocarboxylic acid having 8 to 16 carbon atoms, and salts of these acids; 
 the surfactant comprising a polymerizable surfactant; and 
 a whole amount of the polymerizable surfactant used is not less than 0.5 part by mass and not more than 40 parts by mass, on the basis of 100 parts by mass of the polymerizable monomer being present during said emulsion polymerization. 
 
     
     
       2. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the pigment is a pigment subjected to no hydrophilic treatment. 
     
     
       3. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the pigment comprises at least one pigment selected from the group consisting of C.I. Pigment Red 122 and C.I. Pigment Violet 19. 
     
     
       4. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the polymerization initiator comprises at least one compound selected from the group consisting of 4,4′-azobis(4-cyanovaleric acid) and salts thereof. 
     
     
       5. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the polymerizable surfactant comprises at least one surfactant selected from the group consisting of sulfosuccinic acid ester-based surfactants, alkylphenolether-based surfactants and polyoxyethylene-based surfactants. 
     
     
       6. The process for producing a colored fine particle dispersion according to  claim 1 , comprising the following steps 1 and 2:
 Step 1: dispersing a mixed solution comprising the pigment, the polymerizable surfactant and the water to prepare a dispersion; and 
 Step 2: subjecting the dispersion and the polymerizable monomer to emulsion polymerization in the presence of the surfactant and the polymerization initiator to produce the colored fine particle dispersion. 
 
     
     
       7. The process for producing a colored fine particle dispersion according to  claim 6 , wherein in the step 2, the polymerization initiator is added. 
     
     
       8. The process for producing a colored fine particle dispersion according to  claim 6 , wherein in the step 2, a surfactant is further added. 
     
     
       9. The process for producing a colored fine particle dispersion according to  claim 6 , wherein in the step 1, an amount of the polymerizable surfactant used is not less than 1% by mass and not more than 50% by mass, on the basis of the pigment. 
     
     
       10. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the surfactant comprises at least one anionic surfactant selected from the group consisting of fatty acid salts, alkylbenzenesulfonic acid salts, polyoxyethylene alkylphenylethersulfuric acid ester salts, polyoxyethylene aralkylarylethersulfuric acid ester salts and polyoxyethylene alkylethersulfuric acid ester salts. 
     
     
       11. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the polymerizable monomer comprises a hydrophobic vinyl-based monomer that comprises at least a hydrophobic group and a polymerizable group in a structure thereof, the hydrophobic group comprises at least one group selected from the group consisting of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group, and the polymerizable group comprises at least one group selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group and a vinylene group. 
     
     
       12. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the polymerizable monomer comprises an ionic monomer, and the ionic monomer comprises at least one anionic monomer selected from the group consisting of carboxylic acid monomers, sulfonic acid monomers and phosphoric acid monomers. 
     
     
       13. A process for producing a water-based ink for ink jet printing, comprising the step of mixing the colored fine particle dispersion produced by the process according to  claim 1  and an organic solvent B. 
     
     
       14. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the surfactant further comprises at least one nonionic surfactant selected from the group consisting of polyoxyethylene alkyl phenyl ethers, polyoxyethylene aralkyl aryl ethers and polyoxyethylene alkyl ethers. 
     
     
       15. The process for producing a colored fine particle dispersion according to  claim 1 , wherein the polymerizable surfactant comprises at least one compound selected from the group consisting of compounds represented by formula (I) and formula (II), 
       
         
           
           
               
               
           
         
         wherein BO is a butyleneoxy group; EO is an ethyleneoxy group; M is a cation; m represents an average molar number of addition of BO, and is a number of not less than 1 and not more than 10; and n represents an average molar number of addition of EO, and is a number of not less than 4 and not more than 25; 
       
       
         
           
           
               
               
           
         
         wherein M 2  is a cation; R is a hydrocarbon group having not less than 8 and not more than 14 carbon atoms; and p represents an average molar number of addition of (CH 2 CH 2 O), and is a number of not less than 4 and not more than 15.